The sub-aquatic caverns of Mexico's Yucatan peninsula have long been a favorite spot for divers and cave explorers, but thanks to San Diego-based PassmoreLab, soon everyone will be able to catch a glimpse of one of nature's most beautiful phenomena.

Inner Earth, an educational film series on cave formations and their uses throughout history will use PassmoreLab technology to film the Ox Bel Ha and Nohoch Nah Chich cave systems in Mexico's Yucatan Peninsula. Ox Bel Ha is the world's longest underwater cave and Nohach Nah Chich is the third longest. Both caves used to be above the water's surface until rising oceans submerged them.

PassmoreLab founder, Greg Passmore, has a more humanist take on the importance of the cave film project. "For whatever reason, people have always been drawn to caves. Through the ages, caves have been used as places of refuge, religious ceremony and awe. These underwater caves are fascinating places that touch our imagination. Inner Earth will allow all of us to experience a world which until now only a few people have ever seen."

Filming difficult locations like the 83-mile-long Ox Bel Ha is nothing new to PassmoreLab. Because of its unique ability to create camera systems that can film
where no one else has filmed before, the company has been involved in film projects throughout the world. "We help to see things in new and powerful ways through science," says Passmore.

PassmoreLab is currently producing thirteen heart-stopping episodes of Inner Earth, showcasing the largest and most amazing caves on the planet. The show brings its audience caves filled with ice, crocodiles, remains of ancient cities, massive bat colonies and even caves flooded with water. Some caves are so large they are explored with helicopters. Others are so tight breathing is difficult. Educational and entertaining, Inner Earth also explores the relationship between our culture on the surface and the world inside the earth.

About PassmoreLabPassmoreLab started in San Diego in 2003. The company's staff is comprised of programmers and scientific engineers. The company also employs several graphic artists, videographers, a musical composer and even a biologist. PassmoreLab facilities include a full studio, post production facilities, an optical development lab and a software development environment. PassmoreLab is a firm with staff around the world in San Diego, South Africa and Russia.

According to <a href="http://www.speleonet.com">speleonet.com</a>, a website for cave divers, these caves represent "an irreplaceable resource. [Their] scientific study has already yielded vital environmental information important not only in a local sense, but in a broader global perspective as well... The understanding of what's going on underground is an essential tool in helping to make sagacious decisions as to what should and should not happen on the surface."

Both caves used to be above the water's surface until rising oceans submerged them.

Sigh. This is a misleading statement, as it suggests that the caves formed with air in them. That is not true. This a common misunderstanding of many caves, but I see this type of statement allot in relation to the Yucatan caves.

The caves formed underwater, acting like underground rivers. However in the past, sea levels have been lower than they are currently because of all the water frozen at the poles and in glaciers. During one of those past glacial periods, sea level was lower and many of these coastal caves ended up being drained, and speleothems formed in them.

We are currently at a relatively high sea level, and so these older caves with the speleothems have been reflooded. Some parts of the cave are actively being eroded out again making even more underground rivers. However the parts of the cave with all the speleothem decorations are older than at least 1 glacial cycle, and possibly many more. I would suggest that some parts of the caves are at least 2-3 glacial cycles old but this remains to be quantified using U/Th dating. This cycle of formation-draining-reflooding is why the Yucatan caves are called polygenetic, they have had more than 1 formation cycle overprinted on top of what was there before. It makes studying the geomorphology and hydrology a very fun topic, and very distinct from the situation in continental caves.

One of the reasons that the caves along the Caribbean coast of the Yucatan have experienced so many flooded-drained-flooded cycles is that the peninsula appears to be fairly stable in its vertical position relative to sea level. The Yucatan peninsula has not been uplifted like the islands of Guam, Isla de Mona, and others have been. When a karst coastline is uplifted, the caves are literally lifted up and out of the water by geological processes leaving the caves perched up on the escarpment faces. Those perched caves will never be subjected to the reflooding that the Yucatan caves are.

It is also worth mentioning that the cenote sinkholes of the Yucatan - especially on the Caribbean side - are a feature directly related to this formation-draining-reflooding cycle. Most cenotes are just sections of the cave where the roof has collapsed. This happens easily enough when the sea level drops, as the buoyant support of the water is lost and the ceiling just can't support itself in air. When the sea level rises again, the collapse is filled with water making a pretty water filled cenote.

Sorry - I didn't mean to write so much. I know that the original posting was just pointing to a press release. Hope you enjoyed some of this.

The whole thing of studying sea level fluctuation thru caves near or below present sealevel is fascinating: try googling Sea Level High Stands for info. I learned alot on this topic from John Mylroie in the Bahamas last year.

There was an interview with Canadian cave-diver-guide Dennis Weeks on the Mayan Riviera in The Canadian Caver #69.